Which physical property refers to the temperature at which substance in a solid state transforms to a liquid state?

What does x represent in the formula for the compound xcl4?

Great amounts of electromagnetic energy from our sun and other bodies in space travel through space. which is a logical conclusion about these electromagnetic waves? their energy must be very their frequency must be very low these waves can travel without a medium they only travel through a vacuum of space

Which of the following represents the ester functional group? a. -coo- b. -cho c. -cooh d. c=o